Currently, short-range communication of up to one kilometer is largely dependent on infrastructure-intensive cellular networks, direct radio frequency or optical signaling. However, in regions lacking such infrastructure and points of communication are separated by obstructions, these traditional methods of communication are inadequate. Additionally, traditional optical and radio frequency communication are prone to interference associated with conditions such as environmental scatter and other signals. In situations where confidential information is to be communicated, existing methods of information transmission rely on data encryption since the transmitted signals are subject to eavesdropping. These problems have previously been so intractable in the area of secure communication that business, governmental, and military units often resort to couriers for the short-range transport of such messages. The use of a courier is an incomplete solution that is cumbersome and slow, especially when a geographic or manmade obstacle is involved.
In an effort to address these limitations, others have looked to optical communication. There have been reports of U.S. Navy research on intentionally short-range optical communications [5]. Many solar-blind UV systems were reported on, including an ultraviolet (UV) laser system that showed 500 m non-line-of-sight (NLOS) digital data transmission in field tests. Unfortunately, the reported transmissions were not of a secure nature.
Thus, there exists a need for a short range, secure communication that is not dependent on line-of-sight. An additional need exists for a communication system that is tolerant of environmental scattering as the signal propagates there through.